A closing apparatus is known from DE 103 42 596 B3.
A closing apparatus for a withdrawable-part rack, which is also known under the name shutter, serves the purpose of preventing contacts (which are in the form of contact blades, for example) on the rear wall of the withdrawable-part rack being unintentionally touched by persons located on site when the withdrawable-part rack is open, i.e. when no circuit breaker has been inserted, and to prevent these people then from receiving an electric shock, which may be fatal. For this purpose, at least two plates with openings are provided (in the case of DE 103 42 596 B3 three plates), in a closed state of the closing apparatus the openings of each plate being covered by in each case another plate and in an opened state of the closing apparatus openings of all of the plates lying over one another.
In the closed state the plates therefore effectively cover the contacts (contact blades). In the open state, the entire plate arrangement can be moved over the contact blades, naturally with the proviso that the openings lie over one another with a precise fit. In order to lie the openings of the plates over one another, at least one plate needs to be displaceable (with respect to the other plates), for which purpose a special mechanism is provided which can be actuated by an inserted circuit breaker. The reason for this is that, during insertion of a circuit breaker, there is no longer any risk for operating personnel, in fact the risk would be even greater if the operating personnel would have to actuate the mechanism themselves.
The mechanism in DE 103 42 596 B3 is such that two V-shaped rod assemblies are provided, of which in each case the two limbs are connected to one another via an articulated joint (which can also be expressed as the two limbs being mounted in the articulated joint so as to be capable of a rotary movement). The articulated joint makes it possible for the rod assembly to spread apart (enlargement of the angle of the limbs with respect to one another). The free end of one of the limbs is connected to a plate to be displaced in each rod assembly. In principle it is possible for the free end of the other limb as well to be connected to another plate to be displaced, but in DE 103 42 596 B3 in each case one of the two limbs of the two V-shaped rod assemblies is fixed.
In the closing apparatus from DE 103 42 596 B3, a telescopic rod backs on the two articulated joints. The reason for the use of the telescopic rod is that a fixed connection between the articulated joints is not possible because the articulated joints move perpendicular to the insertion direction of the circuit breaker when the rod assembly is spread apart and in the process in particular the distance between them is enlarged. The telescopic rod now has a variable length.
It has proven to be disadvantageous that during the transition from the closed state to the open state the telescopic rod needs to be extended. In particular, the circuit breaker presses on the telescopic rod in the insertion direction, while the telescopic rod needs to perform its extension movement in the perpendicular direction thereto. This involves relatively high frictional forces, and the effect of these frictional forces is increased by virtue of the fact that considerable lever effects are achieved as a result of the presence of the V-shaped rod assembly.